Jet Fuel Thermal Oxidation Test Equipment

ABSTRACT

Jet fuels&#39; thermal oxidation characteristics are evaluated via the Standard Test Method for Thermal Stability of Aviation Turbine Fuels. This test method mimics the thermal stress conditions encountered by jet fuel in operation and is often carried out by laboratory devices, known as rigs. The rigs include a test section having a sleeve and a heater tube arranged therein. A pair of bus bars secure the test section to the rig and apply a current to the heater tube. The applied current heats the heater tube and subjects the sample jet fuels that are flowing in the volume between the sleeve and heater tube to high temperatures, which may produce thermal oxidation deposits on the heater tube. Heater tubes are difficult to install, however, and a gauge may be used to ensure accurate placement of the heater tube within the sleeve. In addition, the fuel sample must be prepared via an aeration process, and systems are disclosed for automating the aeration process such that the sample is prepared precisely according to the test standard. Moreover, the rig includes a pump system that moves the fuel sample through the test section, and a pump system is provided in a double syringe arrangement that optimizes fuel flow through the test section without fluctuation. Finally, the rigs include cooling systems for cooling the bus bars and maintaining an appropriate thermal profile within the heater tube, and cooling systems may be provided that independently control the temperature of each bus bar.

FIELD OF INVENTION

The present disclosure is related to jet fuel thermal oxidation testingand, more particularly, to equipment that may be used with jet fuelthermal oxidation testing rigs to improve accuracy, efficiency, andreliability.

BACKGROUND

Modern jet engine systems comprise gas turbine engines that run on jetfuel. Under normal operating conditions, jet fuel is heated by the hotcomponents or regions of the gas turbine engines, which include the fuelnozzles, fuel nozzle support assemblies, and heat exchangers. Modern jetengine systems use the jet fuel's heat sink capability for coolingvarious aircraft systems, including hydraulic, electronic, andlubrication systems. However, heat management and, ultimately,performance of the jet engine system and airframe is a delicate balancebetween (i) running fuel systems cooler and incurring performance, cost,and weight penalties by use of air cooling, or (ii) running systems ashot as possible and causing problems associated with unacceptabledeposition rates. Accordingly, engineers often design jet engine systemsto take maximum advantage of the thermal stability of currentlyavailable fuels.

Trends in higher whole engine system performance as well as airframe andengine heat loads, coupled with simultaneous reductions in fuelconsumption, are forcing fuel system temperatures to increase evenfurther. Therefore, many modern high performance jet engine systemsutilize thermally stressed fuels. At high temperatures, however, lessstable species in the thermally stressed jet fuel may undergo oxidationreactions that produce gums, lacquers, particulates, and coke deposits.These resultants may cause a number of problems, including blockage offilters, loss of heat exchanger efficiency, stiction or hysteresis ofsliding components in control units, and fouling of injectors anddistortion of spray patterns. For example, oxidation of thermallystressed jet fuel may result in deposits or particulate that blocksengine fuel nozzles, thereby causing damage to the engine hot sectionsdue to distorted fuel spray patterns, especially the combustor region.Accordingly, a jet fuel's thermal stability is critical to achievingoptimum performance of modern gas turbine engines.

The current standard for evaluating a jet fuel's thermal oxidation isthe Standard Test Method for Thermal Stability of Aviation TurbineFuels, designation D3241, IP323, as published by the American Societyfor Testing and Materials International (“ASTM International”). Thistest method mimics the thermal stress conditions encountered by jet fuelin operation and, despite being developed in the early 1970s, remainsthe best method to evaluate jet fuel thermal stability. Morespecifically, the D3241 test method sets forth a procedure for ratingthe tendency of jet fuels to deposit decomposition products within afuel system. The D3241 test method is performed in two (2) phases. Thefirst phase mimics the fuel conditions present during airplane engineoperation, whereas the second phase quantifies the oxidation thermaldeposits formed during the first phase.

Various laboratory devices, known as rigs, have been developed sincethat time to facilitate the D3241 test method. These rigs subject analuminum heater tube to sample jet fuel under conditions mimicking thoseencountered during actual engine operation. However, these rigs aredifficult to use and require substantial expertise when installing theheater tube within the test section and when preparing the jet fuelsample. Moreover, these known rigs include pump systems that move thefuel sample through the test section, but often have leaks, inconsistentflow rates, and micro-ruptures, and are expensive to operate andmaintain. Furthermore, these known rigs have primitive temperaturecontrol systems that impact the test results and reproducibility of thesame.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent disclosure, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, withoutdeparting from the scope of this disclosure.

FIG. 1A is a perspective view of an example rig that may incorporate theprinciples of the present disclosure.

FIG. 1B is a detailed perspective view of the example rig of FIG. 1A,showing an example test section that may incorporate the principles ofthe present disclosure.

FIG. 2 is a side view of a disassembled test section utilized in the rigof FIG. 1B.

FIG. 3A is a detailed side view of the sleeve and heater tube assemblyutilized in the test section of FIG. 1B and illustrates the fluid outletwhen the heater tube is arranged within the sleeve.

FIG. 3B is a cross-sectional side view of the fluid outlet of FIG. 3A.

FIGS. 4A-4B are side views of the sleeve and heater tube assembly ofFIG. 3A and illustrate utilization of a gauge to position the heatertube within the sleeve.

FIG. 4C is a cross-sectional side view of the gauge of FIGS. 4A-4B,which may be used to position the heater tube within the sleeve.

FIG. 5 is a schematic that illustrates various functions of the rig ofFIG. 1A that are utilized to aerate the fuel sample.

FIG. 6A is a diagram that illustrates an example operation of a manualfuel sample aeration procedure.

FIG. 6B is a diagram that illustrates an example operation of anautomatic fuel sample aeration procedure.

FIG. 7 is a schematic illustrating an example operation of a pump systemhaving a dual syringe arrangement.

FIG. 8 is a diagram illustrating the operation of a heating systemutilized in the rig of FIG. 1A.

FIG. 9A is a diagram illustrating the operation of a bus bar coolingsystem utilized in the rig of FIG. 1A.

FIG. 9B is a schematic of the bus bar cooling system of FIG. 9A.

FIG. 10 is schematic illustrating an example operation of a bus barcooling system that independently controls the separate bus bars.

FIG. 11A is a schematic illustrating clamping systems that may beutilized to secure the sleeve and heater tube assembly to the bus bars,for example, at the lower bus bar of FIG. 1B.

FIG. 11B is a schematic illustrating an alternate clamping system thatmay be utilized to secure sleeve and heater tube assembly to the busbars.

DETAILED DESCRIPTION

The embodiments described herein provide positioning gauges forarranging a heater tube within the sleeve of a rig test section. Otherembodiments described herein provide air control systems that provideautomated aeration of fuel samples with automatic airflow control.Further, embodiments described herein provide pump systems having doublesyringe arrangements. Moreover, embodiments described herein providecooling systems that independently control the separate bus bars.

The ASTM International jet fuel thermal oxidation test (D3241, IP 323)standard test method (the “test method”) is performed in two (2) phases.The first phase mimics the fuel conditions present during airplaneengine operation, whereas the second phase quantifies the oxidationthermal deposits formed during the first part. A technician performs thefirst phase via an apparatus that simulates conditions present in gasturbine engine fuel systems during operation. The apparatus, referred toherein as a rig, includes a test section that generally comprises atube-in-shell heat exchanger that holds a test coupon and directs fuelflow over the test coupon. The second phase consists of inspection ofthe test coupon either via an instrument that automatically measuresthermal oxidation deposit thickness or through visual inspection. Thefollowing disclosure focuses primarily on the first phase of the testmethod and the rigs utilized therein to form the thermal oxidationdeposit.

FIG. 1A is a partial perspective view of an exemplary rig 100 that mayincorporate the principles of the present disclosure. The depicted rig100 is just one example testing rig that can suitably incorporate theprinciples of the present disclosure. Indeed, many alternative designsand configurations of the rig 100 may be employed, without departingfrom the scope of this disclosure.

In the illustrated embodiment, the rig 100 is configured toautomatically perform the test method; however, it may also beconfigured to automatically perform other petroleum product tests suchas ISO 6249. As illustrated, the rig 100 includes a sample container102, a waste container 104, and a test section 110 that fluidlyinterconnects the sample container 102 and waste container 104 ashereinafter described. In use, a technician will place a fuel sample Sin the sample container 102 and, upon activating the rig 100 to performthe test method, the rig 100 pumps the fuel sample S from the samplecontainer 102, through the test section 110, and into the wastecontainer 102 upon completion of the test method.

FIG. 1B is a detailed view of the test section 110 of FIG. 1A accordingto one or more embodiments. As illustrated, the test section 110 mayinclude a sleeve 112 with a heater tube 114 (partially obscured fromview in FIG. 1B) hermetically sealed therein. Here, the heater tube 114is secured within the sleeve 112 via a pair of nut assemblies 136 a,136b, however, other assemblies may be utilized to secure heater tube 114within the sleeve 112 without departing from the present disclosure. Thesleeve 112 is hollow and is open at each of its ends 112 a, 112 b(obscured from view in FIG. 1B). The test section 110 also includes afuel inlet 116 and an outlet 118 arranged on the sleeve 112 between theopen ends 112 a, 112 b. The fluid inlet 116 is fluidly connected to thesample container 102 and the fluid outlet 118 is fluidly connected tothe waste container 104. In addition, the test section 110 includes atest filter 120 that is arranged proximate to the outlet 118 at alocation between the outlet 118 and the waste container 104.

FIG. 1B also illustrates the rig 100 comprising a pair of jaws or busbars 122 a, 122 b that are arranged to secure the test section 110 in adesired orientation via a clamping system which is further describedbelow with reference to FIG. 11A. However, alternate clamping systemsmay be utilized, for example, as described with reference to FIG. 11B.As described below, the bus bars 122 a, 122 b supply a controlled highamperage, low voltage current to the heater tube 114, thereby making itpossible to maintain an accurate temperature during the duration of thetest method. Accordingly, the bus bars 122 a, 122 b are directly orindirectly connected to a transformer or other power supply (notillustrated). In some embodiments, the bus bars 122 a, 122 b are madefrom brass or other material having a lower thermal conductivity thanthe heater tube 114 material as hereinafter described. In addition, athermocouple 124 is arranged to provide temperature measurements of thetest section 110 as described below.

FIG. 2 illustrates a side view of the test section 110 when disassembledand detached from the rig 100. As illustrated, the sleeve 112 is hollowand the fuel inlet 116 and outlet 118 are disposed between the open ends112 a, 112 b thereof such that the fuel inlet 116, the outlet 118, andthe open ends of 112 a, 112 b are in fluid commination with each other.FIG. 2 also illustrates the heater tube 114 when extracted from thesleeve 112, as may occur before and after the test method. Asillustrated, the heater tube 114 includes a thin portion 130 interposedbetween a pair of shoulders 132 a, 132 b disposed at opposing ends 134a, 134 b of the heater tube 114. In operation, the heater tube 114 isinserted into and through the sleeve 112, and secured thereto via a pairof clamping nut assemblies 136 a, 136 b that permit a technician toremove the heater tube 114 from the sleeve 112, for example, before andafter performing the test method. In the illustrated embodiment, theclamping nut assemblies 136 a, 136 b each include gaskets, washers,seals and nuts to secure the shoulder 132 a of the heater tube 114 atthe open end 112 a of the sleeve 112 and to secure the shoulder 132 b atthe open end 112 b. It will be appreciated, however, that the nutassemblies 136 a, 136 b may be differently arranged with the same and/ordifferent components without departing from the present disclosure.

The heater tube 114 also includes a thermocouple (obscured from view)arranged inside an interior volume thereof, and the heater tube 114 isresistively heated by conductance via the pair of bus bars 122 a, 122 bthat each clamp a respective one of the pair of shoulders 132 a, 132 bof the heater tube 114. In some embodiments, the heater tube 114 is analuminum (or other metal) coupon controlled at elevated temperature bythe bus bars 122 a, 122 b, over which a fuel sample S is pumped.

As mentioned above, at various points before, during, and after the testmethod, the technician may need to assemble or disassemble the sleeve112 and the heater tube 114. For example, the test method may requirethe technician to precisely assemble the test section 110 (i.e., installthe heater tube 114 within the sleeve 112 without any leakage) beforebeginning the test method and/or to disassemble the test section 110 atthe end of the test method. In addition, the test method may call forthe technician to clean, rinse, and dry the certain components duringthe disassembly phase. Accurate analysis and test method results dependon proper assembly, dismantling, cleaning, rinsing, and drying of thetest method components. Thus, significant technician expertise is neededto properly perform these phases of the test method, which may consume asignificant amount of time and resources.

FIG. 3A-3B illustrates a side view of the heater tube 114 assembledwithin the sleeve 112 and secured therein via the clamping nutassemblies 136 a, 136 b. The test method specifies that the heater tube114 is to be manually positioned within the test section 110 by atechnician. More specifically, the test method specifies that the heatertube 114 should be positioned precisely relative to the sleeve 112, andvisually adjusted to center a lip 302 of the upper shoulder 132 a (ofthe heater tube 114) within an aperture 304 of the fuel outlet 118 asillustrated in FIG. 3A-3B. This arrangement permits the fuel sample Smay flow through the fuel outlet 118 and to other downstreaminstrumentation, such as the differential pressure measurementinstrumentation as hereinafter described.

Once the lip 302 of the upper shoulder 132 a has been centered withinthe fuel outlet 118, the technician will tighten and secure the heatertube 114 within the sleeve 112, for example, via the nut assemblies 136a, 136 b. Tightening the heater tube 114 within the sleeve 112 will helpseal the interior volume through which the fuel sample S flows, however,the resulting clamping forces oftentimes cause unintended repositioningof the heater tube 114 relative to the sleeve 112 such that the lip 302is no longer properly positioned as mentioned above. Consequently, anextreme fine adjustment is required to pre-position the lip 302 of theheater tube 114 to account or anticipate such displacement duringtightening. Accordingly, technicians need significant expertise toproperly install the heater tube 114 within the sleeve 112.

FIGS. 4A-4B illustrate a positioning gauge or gauge 402 that may beutilized to reliably position the heater tube 114 relative to the sleeve112, according to one or more embodiments. The gauge 402 may be providedas an accessory to assist technicians that would otherwise need to relyon the visual location of the lip 302 within the outlet 118 in order toprepare the test section 110. In the illustrated embodiment, the gauge402 is open at a first end 404 thereof, and an inner bore 406 of thefirst end 404 is threaded so that the gauge 402 may be screwed onto anend of the sleeve 112, for example, at a plurality of threads 408arranged at the open end 112 a. In some embodiments, the gauge 402 isopen at a second end thereof, and may include a threaded bore at theforegoing second end that includes the same or differently arrangedthreads, and such arrangements may provide the gauge 402 with theability to be used with various test sections 110. The body of the gauge402 includes a central bore that extends a length through the body, andthe length that the bore extends may be equal to the body length orshorter. In some embodiments, the bore extends through the body for alength that is shorter than the body and, in such embodiments, ashoulder may be provided along the inner bore surface to act as anabutment that inhibits further axial movement of the shoulder 132 a.

FIG. 4C illustrates an example of the gauge 402, according to one ormore embodiments. In the illustrated embodiment, the gauge 402 includesa body 410 that is open at the first end 404 thereof. As illustrated,the body 410 includes a bore 412 extending there-through, from the firstend 404 towards a second end 414 that, in the illustrated embodiment, isnot open. Accordingly, the bore 412 extends into the body 410 throughthe first end 404, but stops at a location 416 interposing the first andsecond ends 404,414. As illustrated, the bore 412 includes the threadedinner bore 406 that extends into the body 410 and terminates at anabutment 418. The bore 412 is also illustrated as including anunthreaded inner bore 420 that extends into the body 410 from theabutment 418 such that the abutment 418 interposes the threaded innerbore 406 and the unthreaded inner bore 420. In the illustratedembodiment, the abutment 418 is arranged as a shoulder that reduces thediameter of the unthreaded inner bore 420 as compared to the threadedinner bore 406; however, in other embodiment, the abutment 418 may beprovided as an a protrusion, ring, or other structure that may or maynot affect the diameter of the unthreaded inner bore 420. Here, thethreaded inner bore 406 is arranged proximate to the first end 404 ofthe body 410 and includes a plurality of threads 422 arranged to meshwith the threads 408 at the open end 112 a of the sleeve 112, whereasthe unthreaded inner bore 416 is arranged to interpose the abutment 418and the second end 414 of the body 410.

In use, a technician positions the first end 404 of the gauge 402towards the open end 112 a of the sleeve 112 in a first direction D1 andscrews the threaded inner bore 406 thereof onto the threads 408 of thesleeve 112 at the open end 112 a. Then, the technician inserts theheater tube 114 in a second direction D2 into the open end 112 b at thebottom of the sleeve 112. After positioning the heater tube 114 withinthe sleeve 112, the technician clamps the heater tube 114 into positionat the bottom end of the sleeve 112, for example, via the nut assembly136 b. Then, the technician removes the gauge 402 and clamps the heatertube 114 into position at the top end of the sleeve 112, for example,via the nut assembly 136 a. Thereafter, the technician may tighten theheater tube 114 into position.

As previously mentioned, the test method is performed in two (2) parts.First, the test rig 100 is used to create the thermal oxidation deposit.Second, a dedicated instrument is utilized to quantify thermal oxidationdeposit formed during the first phase. FIG. 5 illustrates a sequence offunctions 502 performed by the rig 100 during the first part of the testmethod to create the thermal oxidation deposit, according to one or moreembodiments. As illustrated, the sequence of functions 502 includes anaeration step or procedure 504, a pre-filtration step or procedure 508,a bus bar cooling step or procedure, a tube heating step or procedure510, and a differential pressure measurement step or procedure 512. Thebus bar cooling will be detailed below.

The fuel sample S is a fixed volume of fuel and stored in the samplecontainer 102. The rig 100 utilizes a pump system 506 to move or pumpthe fuel sample S at a steady rate from the sample container 102,through the test section 110 and across the heater tube 114, and finallyinto the waste container 104. The fuel sample S may degrade on theheated heater tube 114 to form thermal oxidation deposits that mayappear as a visible film thereon. In addition, degraded materials fromthe fuel sample S may flow downstream from the heater tube 114 and, forexample, be caught in the test filter 120.

Accordingly, the fuel sample S is first prepared by aerating orsaturating it with dry air via the aeration procedure 504. After theaeration procedure 504, the rig 100 subjects the fuel sample S to thepre-filtration step 508, for example, by pumping the fuel sample Sthrough a paper membrane. In one embodiment, the paper membrane of thepre-filtration step 508 is a 0.45-μm membrane filter. The pump system506 then moves fuel sample S at a fixed volumetric flow rate into thetest section 110 through the fluid inlet 116 of the sleeve 112. The fuelsample S flows through the test section 110, between an inner wall ofthe sleeve 112 and an outer wall of the heater tube 114, and exits thesleeve 112 through the outlet 118 thereof. After exiting the sleeve 112,the fuel sample S passes through the test filter 120 and the rig 100performs the differential pressure measurement step 512.

In the illustrated embodiment, the differential pressure measurementstep 512 includes estimating an obstruction rate of the test-filter 120by conducting a differential pressure measurement between the pressurein the lines upstream of the test filter (ΔP+) and the pressure in thelines downstream of the test filter (ΔP−). The obstruction rate,hereinafter referred to as a differential pressure drop (ΔP), across thetest filter 120 is measured by mercury manometer or by electronictransducer. The rig 100 may also include a differential by-pass linehaving a valve that may be selectively opened or closed to facilitateflow of the fuel sample S through the by-pass line. If, for example, thedifferential pressure drop ΔP across the test filter 120 begins to risesharply (and the technician desires to run the full test method), thevalve of the bypass line may be opened in order to finish the testmethod.

As briefly detailed above, the test method requires a technician toprepare the fuel sample S via the aeration procedure 504. Morespecifically, the test method directs the technician to inject dry airin the fuel sample S that is contained in the sample container 102 at arate of 1.5 liters (“L”) per minute (“min”) for 6 minutes prior toperforming the test method. Existing instruments, however, utilizemanual airflow adjustment that may affect or influence the accuracy andreproducibility of the test method results. FIG. 6A illustrates anexemplary aeration procedure 502 comprising a number of manual aerationsequence 602 that is utilized by existing instruments. As illustrated,the manual aeration sequence 602 (sometimes referred to as the aerationphase) begins with providing air A at atmospheric pressure, and thenpumping that air A through a filter 604 at a rate of 1.5 L/min via apump 606. The pre-filtered air A is then subject to a drying process,for example, via an air desiccant 608 and humidity sensor 610, thatcollectively dry and measure the amount of moisture present within theair A. The air A is then directed into a variable area flowmeter 612that is manually adjusted to ensure that the air A is injected into thesample container 102 at the desired rate to ensure adequate aeration. Inthe illustrated embodiment, the air A is directed from the variable areaflowmeter 610 into a diffuser 614 arranged within the sample container102 and, as prescribed by the test method, the diffuser 614 may be acoarse 12-millimeter (“mm”) borosilicate glass dispersion tube. As willbe appreciated, aeration of the fuel sample S results in fumes that arevented from the system via a ventilation system. However, the aerationsequence 602 is manual and, depending on the technician's skill andoperation of the variable area flowmeter 612, the test method resultsmay or may not be accurate.

FIG. 6B illustrates an alternate aeration sequence 622 for automaticallycontrolling the airflow during the test method, according to one or moreembodiments. As with the manual aeration sequence 602, the aerationsequence 622 similarly includes utilization of the filter 604, the pump606, the air desiccant 608, the humidity sensor 610, and the diffuser614 arranged within the sample container 102. However, the aerationsequence 622 is performed automatically so that no manual action oradjustment is required to maintain the desired flow rate, therebyensuring that the flow rate prescribed by the test method isutilized/obtained throughout the aeration sequence 622. In theillustrated embodiment, the aeration sequence 622 thus utilizes anelectronic flowmeter 624 (in lieu of the variable area flowmeter 610 ofthe manual aeration sequence 602), and the pump 606 includes a controlloop or controller 626 associated with the electronic flowmeter 624 tomaintain the desired flow rate as the air A is pumped through the airdesiccant 608 and the humidity sensor 610 during at least a portion ofthe automatically controlled aeration sequence 622. In one embodiment,the controller 626 is a servo control utilizing pulse width modulationto coordinate the operation of the pump 606 and the electronic flowmeter624 such that the fuel sample S is appropriately aerated as prescribed.In other embodiments, however, the automatic airflow control of theaeration sequence 622 may be differently arranged, for example, the pump606 and the electronic flowmeter 624 may include a plurality of sensorsand use logic to maintain the prescribed flow rate.

As detailed above, the pump system 506 moves the fuel sample S at asteady rate from the sample container 102, through the test section 110and across the heater tube 114, and finally into the waste container104. Indeed, the test method prescribes that the fuel sample S shouldflow at a rate of 3 mL/min with a pressure of 500 pounds per square inch(“PSI”). This low flow rate, coupled with the variability of themechanical properties of the fuel sample S (i.e., viscosity, density,etc.), may hinder the ability to use conventional pump systems (i.e.,membrane pumps, piston pumps, etc.) in a reliable manner and thusadversely impact the accuracy of the test method results. Moreover, theflow rate may impact the quality of the thermal oxidation deposit formedon the heater tube 114. For example, at a low flow rate period, followedby a sharp increase in flow rate along with a large temperature gradientmay result in axisymmetric instabilities (i.e., Taylor type toroidalvortices) near the hot surface, and these “local vortices,” while notmaking the overall flow through the heater tube 114 turbulent, mayoperate to remove thin layers of the thermal oxidation deposit from theheater tube 114 (as it forms thereon). Thus, the pump system 506utilized should provide a smooth and steady rate of flow so as to notdamage the resulting thermal oxidation deposit.

In the past, conventional pump systems 506 have comprised a singlesyringe, meaning that the whole fuel volume (i.e., the fuel sample S)necessary for the test was contained in the single syringe. Thisgeneration of instrument, however, had numerous issues related to thesize of the syringe, as well as its handling and leaking. For example,where the single syringe is utilized having a volume that is less thanthe total volume of sample fuel S needed for the test method, a pause orgap in flow is inevitable at the time of the intermediate aspirations.Other prior pump systems 506 have utilized high-performance liquidchromatography (“HPLC”) pumps with dual pistons. HPLC pumps, however,are not satisfactory because there are micro ruptures at the end of eachpiston cycle. In addition, HPLC pumps are expensive to purchase andmaintain.

In one embodiment, the pump system 506 has a dual syringe arrangementthat ensures steady flow of the fuel sample S, regardless of themechanical properties of the fuel sample S. FIG. 7 illustrates a pumpsystem 702 utilizing a dual syringe/piston arrangement, according to oneor more embodiments. As illustrated, the pump system 702 includes two(2) syringes or piston assemblies 704,706 that are respectively operatedby a pair of motors 708,710. Thus, the first motor 708 operates to drivethe first syringe assembly 704, whereas the second motor 710 operates todrive the second syringe assembly 706.

In the illustrated embodiment, each syringe assembly 704,706 includes abarrel 712 that is hollow and defines an interior volume 714 into whichthe fuel sample S may be pumped. The barrel 712 includes a tip portion716 at a first end of the barrel 712 and an open end 718 at a second endof the barrel 712 that is oriented opposite of the tip portion 716. Eachsyringe assembly 704,706 also includes a plunger (or piston) 720 thatextends into the interior volume 714 of the barrel through the open end718 thereof, and may slide therewithin so as to increase or decrease theamount of the fuel sample S that may fill the interior volume 714. Thepiston 720 includes a head portion 722 and a shaft 724 that is connectedto a rear face of the head portion 722. The head portion 722 isdimensioned to fit within the interior volume 714 such that its outerperimeter or periphery abuts an interior wall of the barrel 712, therebyforming a seal between the periphery of the head portion 722 and theinterior wall of the barrel 712 to inhibit the fuel sample S fromleaking or flowing out of the open end 718 of the barrel 712. The shaft724 extends away from the rear face of the head portion 722, through theinterior volume 714 and exits the barrel 712 via the open end 718.

In addition, the shaft 724 includes an end 726 that is arranged oppositethe head 722 and operatively coupled to one of the motors 708,710. Inone embodiment, the motors 708,710 are step motors that each include aball screw transmission 728, that in turn drive the piston 720. In thatembodiment, the ball screw transmissions 728 are connected to the end726 of the shaft 724 to drive the head 722 of the plunger relative tothe barrel 712, thereby varying the size of the interior volume 714. Thefeed speed of the piston 720 is imposed by the motors 708,710 via theball screw transmission 728.

Each syringe assembly 704,706 also includes a pair of check valves730,732 to control the flow of the fuel sample S entering and exitingthe interior volume 714 of the barrel 712. Here, the check valves730,732 are arranged at each tip portion 716. The first check valve 730is arranged on an input line 734 that fluidly interconnects the samplecontainer 102 to the interior volume 714 of the barrel 712, and permitsflow of the fuel sample S from the sample container 102 into theinterior volume 714 of the barrel 712, but not in the reverse direction.Similarly, the check valve 732 is arranged on a fluid output line 736that fluidly interconnects the interior volume 714 to other downstreamsystems such as those utilized in the pre-filtration step 508, andpermits flow from the barrel 712 to such downstream equipment, but notin the reverse direction.

The syringe assemblies 704,706 operate with an alternate firingsequence. For example, when the first syringe assembly 704 is drawingthe fuel sample S into its respective barrel 712 (i.e., the suctionphase), the second syringe assembly 706 is expelling the fuel sample Sfrom its respective barrel 712 (i.e., the expulsion phase). With thisarrangement, one of the syringe assemblies 704,706 is always performingan expulsion phase, thereby ensuring that the fuel sample S is providedto the downstream equipment at a constant flow rate, as prescribed bythe test method.

The fuel sample S is drawn into and expelled out of the barrels 712, viaaxial movement of the piston 720, in and out of the barrels 712. Whenthe piston 720 is pulled from the first syringe assembly 704 in a firstdirection X1 at a constant speed, a volume of the fuel sample S issucked from the sample container 102. At the same moment, the piston 720of the second syringe assembly 706 is pushed into the barrel 712 at afixed speed. When pushing the piston 720 into the second syringeassembly 706, the fuel sample S in the respective barrel 712 is expelledat a rate that is dependent on the diameter of the head portion 722 andthe speed at which it is displaced within the interior volume 714. Thepair of check valves 730,732 ensure the alternating operation of thesuck phase and the expulsion phase as detailed above and, in someembodiments, the pair of check valves 730,732 are active valves, whereasin other embodiments the pair of check valves 730,732 are passivevalves.

The pump system 702 pumps the fuel sample S with an imperceptible flowfluctuation during the switch from one of the syringe assemblies 704,706to the other. This is achieved by accelerating one of the pistons 720 atthe beginning of its stroke in the bottom of the barrel 712 (i.e.,proximate to the open end 718), as it travels in the first direction X2towards the tip 716 and simultaneously decelerating the second piston720 when it nears the end of its stroke (i.e., proximate to the tip716). Thus, the deceleration of one piston 720 (e.g., of the firstsyringe assembly 704) at the end of the cycle is compensated by theacceleration of the other piston 720 (e.g., of the second syringeassembly 706), and vice versa. This phasing is provided such that thesum of the piston 720 speeds of the first and second syringe assembly704,706 is always equal to the nominal feed rate, thereby ensuring aconstant rate of flow rate for the chosen diameter of the barrel 712. Inthe illustrated embodiment, the interior volume 714 of each barrel 712is 5 mL, and the fuel sample S flow rate is 3 mL/min. In the illustratedembodiment, the switch period from one of the syringe assemblies 704,706to the other is about 20% of the total cycle time, which therebyeliminates any flow fluctuation.

As the fuel sample S is pumped through the test section 110, a steadycurrent is applied to the heater tube 114 via the bus bars 122 a, 122 band, depending upon the temperature and/or quality of the fuel sampleutilized in a particular test, a thermal oxidation deposit may form onthe heating tube 114 as a visible film. The heater tube 114 ismaintained at a relatively high temperature, for example, at 260° C.;however, this temperature may be higher or lower in some applications.The current applied to the heater tube 114 is controlled to maintain asteady temperature at the point of measurement.

FIG. 8 is a diagram that illustrates a conventional heating system 802for heating the heater tube 114 via the bus bars 122 a, 122 b. Asillustrated, the conventional heating system 802 includes a power supply804, a control system 806, a thermocouple 124 that measures a hot spot808 of the heater tube 114 at a point P thereon, and the pair of busbars 122 a, 122 b that secure the heater tube 114. The heater tube 114is resistively heated by the conductance of high amperage, low voltagecurrent from the power supply 804 through the heater tube 114, whichresults in the heater tube 114 having a thermal profile as illustrated.Here, the position of the point P of measurement of the thermocouple 124is located inside the heater tube 114, and is fixed by the length of theshoulder 132 a,b of the heater tube 114, which per the test method is 39mm. Therefore, this 39 mm point is in the hottest region (i.e., the hotspot 808) of the heater tube 114 utilized in the test method.

In the illustrated embodiment, the bus bars 122 a, 122 b are relativelyheavy and water-cooled so that they incur a relatively minimaltemperature increase when supplied with current. The control system 806serves as an indicator and/or controller. For example, it mayautomatically control the temperature and vary the power supplied fromthe power supply 804 as needed so that a steady source of heat isprovided to the bus bars 122 a, 122 b and heater tube 114. Accordingly,the heating system 802 may be utilized to maintain a target temperature,for example, 260° C., as prescribed by the test method. The controlsystem 806 may alternatively provide for manual operation and thusprovide a technician only a temperature readout so that he or she maymanually adjust the temperature as needed.

The thermal profile of the heater tube 114 and, therefore, the positionof the hot spot 808 thereon, may be influenced by numerous factors.These factors include the thermal properties of the fuel sample S, thetemperature of the bus bars 122 a, 122 b, and the temperature difference(ΔT) between the bus bars 122 a, 122 b. In addition, the ability tocontrol the thermal profile of the heater tube 114 may improve testmethod results and reproducibility of the same. Conventionalinstruments, however, do not include control systems that permitfine-tuning of the heater tube 114 thermal profile. For example, whileexisting instruments do include cooling systems that remove heat goinginto the bus bars 122 a, 122 b by conduction from the hot heater tube114, technicians may not control these existing cooling systems tooptimize the heat profile of the heater tube 114.

The bus bars 122 a, 122 b of existing rigs 100 are cooled via watercooling systems that circulate water along a single path that flowsthrough each bus bar 122 a, 122 b. The water may be provided from anexternal source, for example a laboratory sink, or existing instrumentsmay include an internally circulated and radiator cooled water system tocirculate water. FIG. 9A is a diagram illustrating how an existing busbar water cooling system 902 operates, and FIG. 9B illustrates anexemplary internal cooling system 904 that may be integrated into theexisting instruments. These existing systems, however, are nottemperature controlled, as they simply include a liquid pump 906 thatcirculates a liquid through the bus bars 122 a, 122 b and then into aheat exchanger 908 that is associated with a fan 910 that blows air atambient temperature, thereby cooling the liquid.

During operation of existing instruments, the initially unheated fuelsample S is introduced into the sleeve 112 proximate the lower bus bar122b, is heated along the length of the heater tube 114 while flowingupward there-along, and exits the sleeve 112 proximate to the top busbar 122 a at a higher temperature. Fuel samples S comprising fuels withgood heat transfer properties will, however, decrease the temperature ofthe lower bus bar 122 b, but such fuel samples S will not impart thesame effect to the upper bus bar 122 a. This will in turn affect theheat profile of the heater tube 114, for example, by skewing the size ofthe hot spot 808 and/or by moving the hottest point P even closer to theupper shoulder 132 a. These effects may adversely impact the test methodresults, as the temperature control system 806 is designed to taketemperature measurements from a single point that is supposed to be thehottest point P on the heater tube 114; however, when the temperatureprofile is skewed and the hottest point P is shifted upwards along theheater tube 114, the temperature control system 806 will no longer bemeasuring the hottest point P, and will therefore provide inaccurateresults. Moreover, when performing successive tests, for example, whenseveral tests are performed in quick succession, the cooling fluid maybecome warmer and the thermal conditions of the heater tube 114 will notbe identical for each of the subsequent tests.

FIG. 10 illustrates a temperature system 1002 for controllingtemperature in the bus bars 122 a, 122 b, according to one or moreembodiments. The temperature system 1002 individually controls thetemperature of each of the bus bars 122 a, 122 b such that they arecontrolled independently of each other, thereby maintaining a constantthermal profile of the heater tube 114. In this way, the temperaturedifference (ΔT) between the bus bars 122 a, 122 b may be minimizedand/or locked or set to a desired value. In addition, by locking thetemperature difference (ΔT) between the top and bottom bus bars 122 a,122 b, the temperature system 1002 may also limit the effects of thevariability of the thermal properties of the tested fuel samples S.

The temperature system 1002 maintains a constant thermal profile of theheater tube 114 as a function of the test method temperature (e.g., 260°C. according to the test method). To do this, the temperature of eachbus bar 122 a, 122 b is perfectly controlled, and their temperatureprofiles are based on a typical temperature profile extracted fromexisting instruments in order to guarantee perfectly correlated results.The reproduced profile is the image of tests performed under normalambient temperature and non-successive testing conditions. Moreover, ifthe test method protocols change or evolve in the future to require, forexample, that the upper and lower bus bars 122 a, 122 b maintain thesame temperature (e.g., 35° C.), the temperature system 1002 will becompatible with such a new requirement while the existing instrumentsutilizing liquid circulation will be unable to satisfy such newrequirement.

As illustrated, the temperature system 1002 includes an upper bus barsub-system 1004 and a lower bus bar sub-system 1006 that control thetemperature in the upper and lower bus bars 122 a, 122 b, respectively.Each of the bus bar sub-systems 1004,1006 includes a cooling module1010, a heat sink 1012, a controller 1014, a forced convection device1016, and a thermocouple 1018 that measures the temperature of itsrespective bus bar 122 a, 122 b. In the illustrated embodiment, thecooling module 1010 is a Peltier element and the forced convectiondevice 1016 is a fan, but other cooling modules 1010 and/or forcedconvection devices 1016 may be utilized without departing from thepresent disclosure. As will be appreciated, each of the bus barsub-systems 1004,1006 include a separate controller 1014 and componentryso that they may individually adjust the heat extracted from the busbars 122 a, 122 b by a respective heat pipe 1008.

Electric power is supplied to the cooling module 1010 and, therefore,the amount of thermal energy transferred from the bus bars 122 a, 122 bto their respective heat sink 1012 is controlled by a temperaturemeasurement carried out on each of the bus bars 122 a, 122 b. Themeasuring point utilized for these temperature measurements is locatedon the bus bars 122 a, 122 b at a point that is close to the interfacewith the heater tube 114 and may each, for example, be located at thesame point of measurement as made on bus bars of existing instruments.

The bus bars 122 a, 122 b may have geometries that optimize heattransfer. For example, an exterior profile or shape 1019 of the bus bars122 a, 122 b may be contoured as illustrated so as to be able to use theentire exchange surface of the cooling module 1010. Also in theillustrated embodiment, each bus bar 122 a, 122 b includes a base 1020and a bore 1022 extending inward therefrom, towards a tapered end 1024that holds or secures the heater tube 114; and the heat pipes 1008 areinserted into the bores 1022 of the bus bars 122 a, 122 b. Since thethermal conductivity of the heat pipe 1008 is higher than that of thebus bars 122 a, 122 b (e.g., which may be made from brass), calories aremore efficiently transferred from one end of each bus bar 122 a, 122 bto the other. The temperature difference (ΔT) between their measuringpoints (i.e., the measuring points of the thermocouples 1018) and thebearing surface of the cold face of the cooling module 1010 may bereduced, which improves the efficiency of the cooling system 1002 andthe response time of the control loop. Thus, the temperature system 1002provides independent thermal control of the separate bus bars 122 a, 122b, while eliminating the impact of ambient temperature compared to acooling solution based solely on heat exchange with the ambienttemperature.

FIG. 11A illustrates a clamping system 1102 that is utilized to securethe lower shoulder 132 b of the heater tube 114 (within the sleeve 112)to the lower bus bar 122 b. As illustrated, the clamping system 1102includes a plate 1104 that is moveably positioned proximate to an endface 1106 of the lower bus bar 122 b, and arranged to compress or clampthe lower shoulder 132 b of the heater tube 114 that is positionedwithin the lower bus bar 122 b. The clamping system 1102 furtherincludes a pair of screws 1108 that extend through an outer surface 1110and interior surface (obscured from view) of the plate 1106 and into theend face 1106 of the lower bus bar 122 b. As will be appreciated, atechnician may tighten or loosen the screws 1108 to compress or depressthe plate 1104 relative to the lower bus bar 122 b. Thus, when the lowershoulder 132 b of the heater tube 114 (that is secured within the sleeve112) is positioned between the interior face (obscured from view) of theplate 1104 and the end face 1106 of the lower bus bar 122 b, thetechnician may tighten or loosen the screws 1108 to secure or remove thetest section 110. In some embodiments, either or both of the interiorface (obscured from view) of the plate 1104 and the end face 1106 of thelower bus bar 122 b are contoured to receive the lower shoulder 132 b ofthe heater tube 114. In addition, the screws 1108 may include a lever1112 extending therefrom to facilitate tightening and loosening of thesame. It will be appreciated that, while note illustrated, the clampingsystem 1102 is similarly arranged at the upper bus bar 122 a tosecure/unsecure the upper shoulder 132 a thereto.

To install or uninstall the sleeve 112 and heater tube 114 assembly(i.e., the test section 110) relative to the lower bus bar 122b, thetechnician must move the plate 1104 so that the plate 1104 no longerobstructs the location on the end face 1106 that receives the lowershoulder 132 b of the heater tube 114. In one method, the technicianmust fully remove one (1) of the screws 1108 and then loosen the otherone (1) of the screws 1108 such that the plate 1104 may pivot on the(remaining) screw 1108, thereby un-obstructing and presenting the lowershoulder 132 b within the end face 1106 of the lower bus bar 122 b.Alternatively, the technician may remove both of the screws 1108 tofully remove the plate 1104 from the end face 1106 of the lower bus bar122 b to install or uninstall the test section 110. While not described,it will be appreciated that the foregoing described operation of theclamping system 1102 may be similarly utilized at the upper bus bar 122a to secure/unsecure the upper shoulder 132 a thereto.

Alternate clamping systems may be utilized, however, that do notnecessitate two (2) screws and that provide improved electrical and/orthermal contact between the shoulders 132 a, 132 b and the bus bars 122a, 122 b. For example, FIG. 11B illustrates a clamping system 1120,according to one or more embodiments. As detailed below, the illustratedclamping system 1120 utilizes a single screw that may be removed toinstall or uninstall the heater tube 114, and may provide enhancedthermal and electrical contact. While the clamping system 1120 of FIG.11B may be utilized with either or both of the upper and lower bus bars122 a, 122 b, it is hereinafter described with use on a singleunspecified bus bar 122 that could be utilized as either the upper orlower bus bar 122 a, 122 b.

As illustrated, the bus bar 122 utilized in the clamping system 1120 isforked at the tapered end 1024. Thus, the tapered end 1024 of the busbar 122 includes a pair of forks or prongs 1122 a, 1122 b extendingtherefrom away from the base 1020 of the bus bar 122. The pair of prongs1122 a, 1122 b define a recess or gap 1124 there-between. Here, gap 1124is sized such that the shoulder 132 a, 132 b of the heater tube 114 maybe inserted or retracted there trough as hereinafter described. Inaddition, the tapered end 1024 may be hollow to define a threaded bore1126 that extends into the bus bar 122 for at least the length of prongs1122 a, 1122 b.

In the illustrated embodiment, the clamping system 1120 further includesa screw 1128 having a threaded portion 1130 that is received within andmeshes with the threaded bore 1126 of the bus bar 122. Also, theclamping system 1120 includes a plate 1132 that is positioned within thegap 1124 between the pair of prongs 1122 a, 1122 b, and the plate 1132is arranged to slide between the prongs 1122 a, 1122 b towards and awayfrom an interior face 1134 of the bus bar 122 that will abut one of theshoulders 132 a, 132 b of the heater tube 114. In operation, one of theshoulders 132 a, 132 b will be disposed proximate to the interior face1134 of the bus bar 122, and the screw 1128 may then be rotated to drivethe threaded portion 1130 thereof into or out of the threaded bore 1126,which in turn drives the plate 1132 towards or away from the interiorface 1134 and thus compresses or decompresses one of the shoulders 132a, 132 b that is positioned there-between. When the screw 1128 and theplate 1132 are withdrawn from the tapered end 1024 of the bus bar 122,the gap will be unobstructed such that the shoulder 132 a, 132 b of theheater tube 114 may be inserted or withdrawn. In the illustratedembodiment, the plate 1132 and the interior face 1134 each include aseat 1132′,1134′ that is contoured to receive the shoulders 1132 a, 1132b′.

Also in the illustrated embodiment, the screw 1128 is hollow andincludes a bore 1136 having a narrow portion 1137a and a wide portion1137b, and the plate 1132 includes a shaft 1138 that is hollow anddefines a bore 1140 that is coaxial with the bore 1136 of the screw1128. As illustrated, the shaft 1138 and its bore 1140 extend from theplate 1132, through the narrow portion 1137 a and into the wide portion1137 b of the bore 1136 of the screw 1128 in a direction away from thebase 1020 of the bus bar 122.

A locking device 1142 maybe be utilized to limit or inhibit the amountof axial movement of the plate 1132 within the gap 1124 relative to thescrew 1128 while permitting rotation of the screw 1128 relative to theplate 1132. The locking device 1142 is secured within the bore 1140 ofthe plate 1132. In addition, the locking device 1142 may include aflange 1144 that floats within the wide portion 1137 b of the bore 1136of the screw 1128, and abuts a shoulder 1146 within the bore 1136 of thescrew 1128 (i.e., that is disposed between the narrow and wide portions1137 a, 1137 b) when the screw 1128 is retracted from the bore 1126 ofthe bus bar 122. Also, the plate 1132 may be attached to the screw 1128to permit relative rotation between the plate 1132 and the screw 1128,but to inhibit the shaft 1138 of the plate 1132 from being fullywithdrawn from the bore 1136 of the screw 1128 via interaction betweenthe flange 1144 and the shoulder 1146. Thus, when the screw 1128 iswithdrawn from the threaded bore 1126 of the bus bar 122, the plate 1132(that is attached to the locking device 1142) will be pulled by the(rotating) screw 1128 in the axial direction away from the base 1020 ofthe bus bar 122. Stated differently, rotation of the screw 1128translates to an axial displacement of the plate 1132 within the gap1124. Accordingly, the plate 1132 is carried by (or retracted with) thescrew 1128, which may be removed from the tapered end 1024 of the busbar 124 to expose the gap 1124 so that the shoulder 132 a, 132 b of theheater tube may be assembled or disassembled relative thereto, whichfacilitates removal of the heater tube 114 from the bus bar 122.

In some embodiments, the bus bars 122 may one or both of a pair ofrecesses 1018 a, 1018 that are disposed at an upper or lower sides ofthe bus bar 122 and arranged to receive one of the thermocouple 1018 ofthe temperature system 1002, as detailed above.

Therefore, the disclosed systems and methods are well-adapted to attainthe ends and advantages mentioned, as well as those that are inherenttherein. The particular embodiments disclosed above are illustrativeonly, as the teachings of the present disclosure may be modified andpracticed in different but equivalent manners apparent to those skilledin the art having the benefit of the teachings herein. Furthermore, nolimitations are intended to the details of construction or design hereinshown, other than as described in the claims below. It is thereforeevident that the particular illustrative embodiments disclosed above maybe altered, combined, or modified and all such variations are consideredwithin the scope of the present disclosure. The systems and methodsillustratively disclosed herein may suitably be practiced in the absenceof any element that is not specifically disclosed herein and/or anyoptional element disclosed herein. While compositions and methods aredescribed in terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps. Allnumbers and ranges disclosed above may vary by some amount. Whenever anumerical range with a lower limit and an upper limit is disclosed, anynumber and any included range falling within the range is specificallydisclosed. In particular, every range of values (of the form, “fromabout a to about b,” or, equivalently, “from approximately a to b,” or,equivalently, “from approximately a-b”) disclosed herein is to beunderstood to set forth every number and range encompassed within thebroader range of values. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee. Moreover, the indefinite articles “a” or “an,” as used in theclaims, are defined herein to mean one or more than one of the elementsthat it introduces. If there is any conflict in the usages of a word orterm in this specification and one or more patent or other documentsthat may be incorporated herein by reference, the definitions that areconsistent with this specification should be adopted.

The use of directional terms such as above, below, upper, lower, upward,downward, left, right, and the like are used in relation to theillustrative embodiments as they are depicted in the figures, the upwardor upper direction being toward the top of the corresponding figure andthe downward or lower direction being toward the bottom of thecorresponding figure.

As used herein, the phrase “at least one of” preceding a series ofitems, with the terms “and” or “or” to separate any of the items,modifies the list as a whole, rather than each member of the list (i.e.,each item). The phrase “at least one of” allows a meaning that includesat least one of any one of the items, and/or at least one of anycombination of the items, and/or at least one of each of the items. Byway of example, the phrases “at least one of A, B, and C” or “at leastone of A, B, or C” each refer to only A, only B, or only C; anycombination of A, B, and C; and/or at least one of each of A, B, and C.

1. A temperature system for independently controlling a temperature of abus bar to improve a thermal profile of a heater tube in a thermaloxidation rig, the temperature system comprising: a heat sink arrangedproximate to a base of the bus bar that secures the bus bar to thethermal oxidation rig, a cooling element that interposes the heat sinkand the base of the bus bar, a forced convection device, a thermocouplearranged at an end of the bus bar that is opposite the base andproximate to the heater tube, wherein the thermocouple measures thetemperature of the bus bar, and a controller that is associated with thecooling element and the forced convection device, wherein the controllercontrols the cooling element and the forced convection device based onthe temperature measured by the thermocouple.
 2. The temperature systemsof claim 1, wherein the base bar includes a bore extending from the basethat receives a heat pipe.
 3. A thermal oxidation rig for analyzing afuel sample, the thermal oxidation rig comprising: a test sectioncomprising a sleeve and heater tube assembly supported by a pair of busbars, wherein the sleeve and heater tube assembly is secured within aclamping assembly arranged in each of the bus bars, wherein the sleeveand heater tube assembly comprises a sleeve, wherein the sleeve ishollow and is open at opposed ends; a heater tube secured within thesleeve and hermetically sealed therein; a fuel inlet and a fuel outletarranged on the sleeve between the open ends of the sleeve; thetemperature system of claim 1 for independently controlling atemperature of a said bus bar to improve a thermal profile of the heatertube in the thermal oxidation
 4. The thermal oxidation rig of claim 3,wherein the bus bar includes a bore extending from the base thatreceives a heat pipe.
 5. The thermal oxidation rig of claim 3, furthercomprising a pumping system for moving the fuel sample from a samplecontainer, into the fuel inlet, and through the test section, thepumping system comprising: a first and second syringe assembly, eachsyringe assembly having a hollow barrel that defines a volume forholding the fuel sample, a tip disposed at an upper end of the barrel,an open end disposed at a lower end of the barrel, each syringe assemblyhaving an inlet valve and an outlet valve; a pair of pistons that areeach arranged to slide within one of the barrel volumes, each pistonhaving shaft that extends into the volume through the open end of thebarrel and connects to a head portion that abuts an interior wall of thehollow barrel so that the volume is sealed from the open end of thebarrel, and a pair of motors, each of the motors is coupled to one ofthe pistons and independently controlled so that a flow rate of the fuelsample remains constant, wherein each of the motors controls a stroke ofits respective piston such that the pistons accelerate and deceleratesimultaneously.
 6. A system for automatically aerating a fuel sample,the system comprising: a pump for facilitating an airflow, an flowmeterthat measures the airflow, and a sample container into which the airflowis injected, wherein the pump further comprises a controller that isassociated with the flowmeter and automatically maintains the airflow ata constant rate via a control loop.
 7. The system of claim 6, whereinthe system further comprises an air desiccant that removes moisture fromthe airflow.
 8. The system of claim 7, wherein the system furthercomprises a humidity sensor arranged to sample the airflow passingthrough the air desiccant.
 9. The system of claim 6, wherein the samplecontainer further comprises a diffuser arranged therein.
 10. The systemof claim 6, wherein the constant rate is 1.5 liters per minute.
 11. Thesystem of claim 6, wherein the system further comprises a filter thatfilters the airflow before passing through the pump.
 12. A gauge forpositioning a heater tube within a sleeve, the gauge comprising a bodyhaving a first and a second end and a bore that extends from the firstend into the body for a length, wherein the bore has a diameter that issized to receive an open end of the sleeve, wherein the heater tubeincludes a pair of shoulders interposed by a thin portion and theshoulders extend away from the thin portion from a lip, and wherein oneof the shoulders extends through the sleeve and into the length of thebore such that lip is positioned proximate to an outlet of the sleeve.13. The gauge of claim 12, wherein the bore of the gauge extends fromthe first end for a length that is shorter than the body.
 14. The gaugeof claim 12, wherein the gauge further comprises a shoulder that isradially disposed along the bore at a location spaced from the first endby a distance equal to the length.
 15. The gauge of claim 14, whereinthe bore extends from the first end to the second end of the body. 16.The gauge of claim 12, wherein a portion of the bore proximate to thefirst end of the body is threaded.
 17. (canceled)
 18. A temperaturesystem for independently controlling a temperature of a bus bar toimprove a thermal profile of a heater tube in a thermal oxidation rig,the temperature system comprising: a heat sink arranged proximate to abase of the bus bar that secures the bus bar to the thermal oxidationrig, a cooling element that interposes the heat sink and the base of thebus bar, a forced convection device, a thermocouple arranged at an endof the bus bar that is opposite the base and proximate to the heatertube, wherein the thermocouple measures the temperature of the bus bar,and a controller that is associated with the cooling element and theforced convection device, wherein the controller controls the coolingelement and the forced convection device based on the temperaturemeasured by the thermocouple.
 19. The temperature systems of claim 18,wherein the base bar includes a bore extending from the base thatreceives a heat pipe.
 20. A clamping system for securing a heater tubeto a bus bar of a thermal oxidation rig, the clamping system comprising:a bore extending into an end of the bus bar and terminating at an innerface of the bus bar; a pair of prongs extending from the inner face tothe end of the bus bar, the prongs defining a gap that extends with thebore; a plate arranged to slide within the gap in an axial direction,and a screw arranged within the bore and coupled to the plate, whereinrotation of the screw translates to displacement of the plate in theaxial direction.
 21. A thermal oxidation rig for analyzing a fuelsample, the thermal oxidation rig comprising: a test section comprisinga sleeve and heater tube assembly supported by a pair of bus bars,wherein the sleeve and heater tube assembly is secured within a clampingassembly arranged in each of the bus bars, wherein the sleeve and heatertube assembly further comprises: a gauge for positioning a heater tubeof the heater tube assembly within a sleeve of the heater tube assembly,the gauge comprising a body having a first and a second end and a borethat extends from the first end into the body for a length, wherein thebore has a diameter that is sized to receive an open end of the sleeve,wherein the heater tube includes a pair of shoulders interposed by athin portion and the shoulders extend away from the thin portion from alip, and wherein one of the shoulders extends through the sleeve andinto the length of the bore such that lip is positioned proximate to anoutlet of the sleeve, wherein the clamping assembly secures the heatertube to the bus bar and further comprises: a bore extending into an endof the bus bar and terminating at an inner face of the bus bar, a pairof prongs extending from the inner face to the end of the bus bar, theprongs defining a gap that extends with the bore, a plate arranged toslide within the gap in an axial direction, and a screw arranged withinthe bore and coupled to the plate, wherein rotation of the screwtranslates to displacement of the plate in the axial direction; apumping system for moving the fuel sample from the sample container andthrough the test section, the pumping system comprising: a first andsecond syringe assembly, each syringe assembly having a hollow barrelthat defines a volume for holding the fuel sample, a tip disposed at anupper end of the barrel, an open end disposed at a lower end of thebarrel, each syringe assembly having an inlet valve and an outlet valve,a pair of pistons that are each arranged to slide within one of thebarrel volumes, each piston having shaft that extends into the volumethrough the open end of the barrel and connects to a head portion thatabuts an interior wall of the hollow barrel so that the volume is sealedfrom the open end of the barrel, and a pair of motors, each of themotors is coupled to one of the pistons and independently controlled sothat a flow rate of the fuel sample remains constant, wherein each ofthe motors controls a stroke of its respective piston such that thepistons accelerate and decelerate simultaneously; an aeration system foraerating the fuel sample in the sample container, the aeration systemincluding a pump, a flowmeter for measuring airflow generated by thepump and injected into the sample container, wherein the pump furthercomprises a controller that is associated with the flowmeter andautomatically maintains the airflow at a constant rate via a controlloop; and a temperature control system of claim 1 for independentlycontrolling a temperature of a said bus bar to improve a thermal profileof the heater tube in the thermal oxidation rig.